This invention relates to solar energy collection, and in particular to an arrangement for driving a row of solar collector assemblies to track the motion of the sun relative to the earth. The invention applies to solar collectors in which the solar collector modules include arrays of photovoltaic cells for generating electrical power, but the same principles can be applied also to arrangements for solar heating, for example.
Photovoltaic arrays are used for a variety of purposes, including as a utility interactive power system, as a power supply for a remote or unmanned site, a cellular phone switch-site power supply, or a village power supply. These arrays can have a capacity from a few kilowatts to a hundred kilowatts or more, and are typically installed where there is a reasonably flat area with exposure to the sun for significant portions of the day.
In general terms, these solar collector assemblies have their solar collector modules, typically photovoltaic modules, supported on a frame. The frame commonly includes a frame member, sometimes referred to as a torque tube or torque member, which serves as an axis. A tracker drive system, also called a tilt assembly, may be used to rotate or rock the solar collector assemblies of the one or more rows of solar collector assemblies about their tilt axes to keep the photovoltaic modules as square to the sun as possible. Usually, the rows are arranged with the tilt axes of the solar collector assemblies disposed in a north-south direction, and the tilt assemblies gradually rotate the one or more rows of solar collector assemblies throughout the day from an east-facing direction in the morning to a west-facing direction in the afternoon. The solar collector assemblies are brought back to the east-facing orientation for the next day.
One solar collector arrangement of this type is shown in Barker et al. U.S. Pat. No. 5,228,924. There, each row of panels is affixed to a horizontal pivot shaft that is supported on two or more support piers on which the pivot shaft is journaled. A drive mechanism is mounted on one of the piers, and pushes against the solar panel at some point that is displaced from the shaft. In that case, the drive is of the screw type, and as a drive motor rotates, a shaft retracts or extends to rotate the row of panels in one direction or the other. In this arrangement, each row of panels has its own respective drive mechanism. Other designs, such as that shown in U.S. Pat. No. 6,058,930, employ a single actuator to control multiple rows of solar panels.